The experimental verification of a towed body and cable dynamic response theory

Measurements of towed body motion in a laboratory towing tank have validated the mathematical model used as a basis for predicting body and cable dynamic behaviour under seagoing conditions.     

Estimation of surface chlorophyll on an exposed mudflat using digital colour-infrared (CIR) photography

The usefulness of field-based digital Colour-InfraRed (CIR) photography to quantify concentrations of chlorophyll on the surface of exposed mudflats is investigated. Multiple images, each 626 mm by 467 mm, were acquired during Austral summertime using a Duncantech three-band CIR camera from two areas of mudflat in the upper reaches of Sydney Harbour. Sediment samples were obtained from within the field of view of the camera and their chlorophyll concentration was estimated spectrophotometrically. After the camera images were normalised to compensate for the effects of variations in the intensity of downwelling solar radiation, chlorophyll was estimated for each 0.9 mm square pixel using a suite of five different vegetation indices. Regression analysis was used to determine the strength of the relationship between the index values and the estimates of chlorophyll from the in situ samples. Indices constructed from near-infrared and red bands were found to have the strongest relationships with in situ chlorophyll estimates (R² ranging from 0.28 to 0.79) and indices derived from near-infrared and green bands the weakest (R² ranging from 0.16 to 0.22). The vegetation indices highlighted complex small-scale variability in chlorophyll distribution that was not evident in the original camera images. These findings indicate that field-based CIR photography will provide a useful tool for the non-destructive determination of benthic chlorophyll.     

Content versus concentration: Effects of units on measuring the biogeochemical properties of soft sediments

A variety of scientific disciplines require measurements of the biological, physical and chemical (biogeochemical) properties of soft sediments. These properties vary temporally and spatially in a highly complex fashion, due to interaction and feedback between the processes that control them. This paper presents theoretical and real examples showing how interaction between the properties of sediments and the use of different units of expression (i.e. content and concentration) can change patterns in the data and thereby alter the interpretation of results. Common mistakes leading to incorrect measurements being taken and incorrect inference of data are presented and a new conceptual way of thinking about natural sediments is discussed. We conclude that the presentation and interpretation of data expressed as concentration is preferable to content for biogeochemical measurements in sediments, because content data is confounded by various factors (including core density/mass), leading to mistaken inference.     

Inversion of Lloyd Mirror Field for Determining a Source's Track

This paper describes a simple approach for inferring the depth and track of a sound source at short ranges by inversion of acoustic field data at a set of sea bottom hydrophones. At short ranges, the acoustic field consists of a dominant Lloyd mirror (LM) signal from the direct and surface-reflected ray paths and a series of bottom-reflected paths that modulate the LM signal. A computationally efficient propagation model based on the method of images is developed to calculate replica fields for the inversion. The matched field inversion method for inferring the source depth and track is demonstrated using data from an experiment carried out in shallow water off the east coast of Canada. The estimated values were in very good agreement with independent measurements taken during the experiment.     

藏南隆子县模麓温泉群水文地球化学特征及成因机制研究

藏南地区地热资源丰富,是喜马拉雅地热带的重要组成部分,有望成为新的地热资源开发靶区。本文以藏南桑日-错那活动构造带内模麓温泉群为研究对象,以水化学和氢氧氚同位素为研究方法,分析模麓温泉群的水岩作用、热储温度、补给来源及径流时间,揭示了地热水的成因机制。模麓地热水pH在6.6～7.2之间,TDS为1 908mg/L～2 326 mg/L,水化学类型以HCO3·Cl-Na型和HCO3·Cl-Na·Ca型为主。地热水中主要阴阳离子来源于硅酸盐矿物的溶解和少量地球深部物质。利用硅-焓方程法和硅-焓图解法计算的初始热储温度为198℃～256℃,冷水混入比例为68%～85%。此外,对地热水中的Li、B、F等微量元素分析得出,研究区温泉水中微量组分除来自水-岩作用外,应该还与深部流体的混入有关,且该地区的氢氧同位素特征表明地下水补给主要来源于大气降水,补给高程为5 652m～5 664m,模麓地热水中的氚含量<0.5TU,表明其地热水为老水,有更长的径流时间,为水-岩作用提供了充足的时间,而宿麦郎曲河水为新水,补给径流时间短。研究区地热水与围岩遮拉组砂板岩发生水-岩作用,进行离子交换作用,在地...     

Analyzing Animal Movement Characteristics From Location Data

When individuals of a species utilize an environment, they generate movement patterns at a variety of spatial and temporal scales. Field observations coupled with location technologies (e.g. GPS tags) enable the capture of detailed spatio‐temporal data regarding these movement patterns. These patterns contain information about species‐specific preferences regarding individual decision‐making, locational choices and the characteristics of the habitat in which the animal resides. Spatial Data Mining approaches can be used to extract repeated spatio‐temporal patterns and additional habitat preferences hidden within large spatially explicit movement datasets. We describe a method to determine the periodicity and directionality in movement exhibited by a migratory bird species. Results using a High Arctic‐nesting Svalbard Barnacle Goose movement data yielded undetected patterns that were secondarily corroborated with expert field knowledge. Individual revisits by the geese to specific locations in the breeding and wintering grounds of Svalbard, Norway and Solway, Scotland, occurred with a periodicity of 334 days . Further, the orientation of this movement was detected to be mostly north‐south. During long‐range migration the geese use the north‐south oriented Norwegian islands as “stepping stones”, Short‐range movement between mudbank roosts to feeding fields in Solway also retained a north‐south orientation.